This paper proposes a method for measuring the stimulated Brillouin scattering （SBS） threshold based on waveform variation of SBS optical limiting. The output waveforms for different pump power densities are numeric...This paper proposes a method for measuring the stimulated Brillouin scattering （SBS） threshold based on waveform variation of SBS optical limiting. The output waveforms for different pump power densities are numerically simulated, and validated in the Nd：YAG seed-injected laser system. The results indicate that SBS does not take place in the case of a low pump power density and thus the output power scales up linearly with pump power. Once the pump power density exceeds the SBS threshold, SBS takes place and thereby the energies are transferred from pump to Stokes. As a result, a small shoulder appears in the trailing edge of the output waveform, which provides another method to determine the SBS threshold.展开更多
This paper investigates the effect of beam divergence angle on output waveform based on stimulated Brillouin scattering optical limiting.Output waveforms in the case of different pump divergence angles are numerically...This paper investigates the effect of beam divergence angle on output waveform based on stimulated Brillouin scattering optical limiting.Output waveforms in the case of different pump divergence angles are numerically simulated,and validated in a Nd：YAG seed-injected laser system.The results indicate that a small pump divergence angle can lead to good interaction between pump and Stokes,and a platform can be easily realized in the transmitted waveform.In contrast,a peak followed by the platform appears when the divergence angle becomes large.展开更多
针对主瓣干扰(main-lobe jamming,MLJ)在空域与有用信号(signal of interest,SOI)高度相关而难以被有效抑制的问题,基于跳变编码波形的抗MLJ系统通过对波形进行编码调制,接收端据此重构接收信号,利用码-空映射等效改变SOI空域信道,实现...针对主瓣干扰(main-lobe jamming,MLJ)在空域与有用信号(signal of interest,SOI)高度相关而难以被有效抑制的问题,基于跳变编码波形的抗MLJ系统通过对波形进行编码调制,接收端据此重构接收信号,利用码-空映射等效改变SOI空域信道,实现SOI与干扰信号在空域的分辨。但理论分析发现,信号带宽的增大将掩盖编码特征并使该方法失效。为此,利用多抽头系统的时-频映射特质,通过多抽头结构设计降低带宽掩盖,重新凸显编码特征。仿真结果显示,所提方法可在10 MHz的全带宽内,使干扰对消比大于20 dB,SOI对消比小于3 dB,具有较好的抗主瓣非零带宽干扰性能。展开更多
随着电力系统的迅速发展,短路电流超标已经成为突出问题。故障电流限制器(fault current limiter,FCL)可以在不改变电网潮流分布的情况下限制短路电流,具有良好的应用前景。如何快速准确地识别出短路故障是故障电流限制器使用效果的关...随着电力系统的迅速发展,短路电流超标已经成为突出问题。故障电流限制器(fault current limiter,FCL)可以在不改变电网潮流分布的情况下限制短路电流,具有良好的应用前景。如何快速准确地识别出短路故障是故障电流限制器使用效果的关键因素之一。针对短路故障发生时线路电流会发生突变这一特性,提出了一种采用线路电流波形曲率对故障电流快速识别的方法。用PSCAD仿真软件建立了华东500 kV电网故障电流限制器等值系统。在该等值系统上对基于线路电流波形曲率的故障信号快速识别方法进行了研究。结果表明该方法对短路电流突变特性有识别能力且对识别速度有提高作用。最后通过伊敏—冯屯可控串补工程现场故障录波数据验证了上述结论。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60778019 and 60878005)the Program for New Century Excellent Talents in University (Grant No NCET-08-0173)the Program of Excellent Team in Harbin Institute of Technology and the Program of Science and Technology of the Education Bureau of Heilongjiang Province,China (Grant No11521048)
文摘This paper proposes a method for measuring the stimulated Brillouin scattering （SBS） threshold based on waveform variation of SBS optical limiting. The output waveforms for different pump power densities are numerically simulated, and validated in the Nd：YAG seed-injected laser system. The results indicate that SBS does not take place in the case of a low pump power density and thus the output power scales up linearly with pump power. Once the pump power density exceeds the SBS threshold, SBS takes place and thereby the energies are transferred from pump to Stokes. As a result, a small shoulder appears in the trailing edge of the output waveform, which provides another method to determine the SBS threshold.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60778019 and 60878005)the Program for New Century Excellent Talents in University of China (Grant No NCET-08-0173)the Program of Excellent Team in Harbin Institute of Technology of China
文摘This paper investigates the effect of beam divergence angle on output waveform based on stimulated Brillouin scattering optical limiting.Output waveforms in the case of different pump divergence angles are numerically simulated,and validated in a Nd：YAG seed-injected laser system.The results indicate that a small pump divergence angle can lead to good interaction between pump and Stokes,and a platform can be easily realized in the transmitted waveform.In contrast,a peak followed by the platform appears when the divergence angle becomes large.
文摘随着电力系统的迅速发展,短路电流超标已经成为突出问题。故障电流限制器(fault current limiter,FCL)可以在不改变电网潮流分布的情况下限制短路电流,具有良好的应用前景。如何快速准确地识别出短路故障是故障电流限制器使用效果的关键因素之一。针对短路故障发生时线路电流会发生突变这一特性,提出了一种采用线路电流波形曲率对故障电流快速识别的方法。用PSCAD仿真软件建立了华东500 kV电网故障电流限制器等值系统。在该等值系统上对基于线路电流波形曲率的故障信号快速识别方法进行了研究。结果表明该方法对短路电流突变特性有识别能力且对识别速度有提高作用。最后通过伊敏—冯屯可控串补工程现场故障录波数据验证了上述结论。
